Electric Aircraft Battery Cooling for Nuncats - case study
Customer profile: Nuncats CIC is a British aircraft company, providing electric aircraft transportation systems in order to replace the petrol engine and fuel tanks.
The electric aircrafts designed and built by Nuncats are based on batteries, supported by solar charging stations on the ground.
The aim is to provide cheap and sustainable transport to rural or remote areas (e.g. to deliver doctors, teachers and medical supplies in Africa), where the roads are unreliable and the conventional ways of transport would fail or it would be extremely expensive.
Together with Nuncats we worked on a project to ensure proper cooling of the battery pack in the aircraft. Using Q-Bat – our battery simulation software, we have analysed the battery pack in several phases of flight. This way we were able to check if the cooling fans were enough to keep the temperatures at desirable levels.
Project challenge and Customer’s expectations:
- safely check the battery behavior during flight conditions,
- need to reduce number of physical prototypes,
- gain insight into physical phenomena that is difficult to observe directly from the experiment,
- predict key process parameters from any location in the region of interest,
- reduce time to market.
Solution we provided:
As QuickerSim we developed software (called Q-Bat) for extremely quick thermal simulations of battery packs of all kinds.
In Nuncats case we performed battery pack thermal simulation methodology that included modeling technical solutions tailored to the customer's newly created product.
The battery pack consisted of 416 cells in a 16s26p circuit configuration, bus bars, resistor and casing. Before starting the simulation, we made a set of the model assumptions. The nickel-based tabs were excluded and modelled by increasing the height of the cells’ terminals. The battery cell was modelled using an R equivalent circuit model, and input parameters were identified based on data provided by the Customer. This model does not take into account cell relaxation time. Despite that, it is sufficient for a simple current load that does not vary in time. Boundary conditions, such as heat transfer coefficients for the simulations were calculated using empirical formulas from the literature. Two main flow regimes were identified and each of them was treated differently. First of them was flow past the cylinders – cells on the bottom and the top floor. The second one was flow perpendicular to the horizontal plate – heat transfer between air and the resistor. To simulate forced convection in the battery pack we performed simulation of the airflow in ANSYS Fluent to obtained velocity field. The airflow through the cylindrical cells is slowed down by them thus we simulate the zones, in which the cells are located, as a porous media. The velocity field was interpolated from Fluent and coupled with components in the Q-Bat using the tetrahedral mesh of the air domain. The simulation results were post-processed to obtain 3D temperature distribution and temperature trend plots of battery pack elements.
Customer’s benefits:
- Reduced design cost due to lower number of physical tests needed,
- Shorter time-to-market thanks to quick simulation results compared to building a prototype
- Improved safety of the battery pack,
- In-depth knowledge about the thermal behavior of the battery pack.
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